Condition monitoring of hydrostatic transmissions by using the volumetric loss method

Condition monitoring is a good way for decreasing maintenance costs of machines, especially when the monitoring system works together with other systems [1], [2]. Worked out at the Technical University of Gdansk the control - monitoring system is an example of such a solution. The system can monitor and control closed circuit hydrostatic transmissions in operating conditions. Wear of hydrostatic transmissions is accompanied by increase in volumetric loss. A continuos or periodic assessment of the volumetric loss provides information of technical worthiness. Values of volumetric loss in a hydrostatic transmission are the sum of values of volumetric loss in the pump and in the motor. The accuracy of the pump displacement measurement and problems with assembling the expensive transducers are the difficulty of such an assessment. The values of the volumetric loss in a hydrostatic transmission are dependent on its operating parameters, particularly on the high pressure oil, pump shaft speed and oil viscosity. The structure of the mathematical models of the volumetric losses in hydrostatic transmission are presented as well as the experimental verification of the models and verification of the monitoring method accuracy.